Emission after treatment devices are utilized to collect particulate matter from the exhaust gas of an internal combustion engine. In particular, conventional emission aftertreatment devices for diesel engines include particulate filters, oxidation catalysts, and nitrous oxide (NOx) catalysts. A problem associated with particulate filters is that the particulates, which consist largely of carbon particles, tend to plug the filters resulting in a restriction to the exhaust gas flow. A conventional method of regenerating/cleaning the filter involves increasing the exhaust gas temperature above a predetermined temperature (e.g., above 450.degree. C.) to incinerate the carbon particles in the filter.
Conventional methods have increased the exhaust gas temperature of an engine by controlling a throttle valve in an intake manifold of the engine. In particular, it is known that by throttling/closing the throttle valve, the exhaust gas temperature may be increased. Further, numerous methodologies have been utilized for controlling the throttle valve. In one conventional method, the intake throttle valve is controlled utilizing the difference between a calculated target intake manifold pressure and an actual intake manifold pressure. The target intake manifold pressure is calculated using an engine speed and an engine load. This conventional method has a drawback of being unable to regenerate the particulate filter during low engine speeds or low engine load conditions because the required amount of throttling would result in unstable engine operation. Accordingly, when the engine is operating during low engine speeds or low engine load conditions, the particulate filter may become clogged creating an undesirable restriction in the exhaust gas flow and allowing increased exhaust gas emissions.
There is thus a need for a method of controlling an exhaust gas temperature of an engine during low engine speeds and/or low engine load conditions to initiate the regeneration of a particulate filter or the like.